DARWINISM ATTACKED. 43 



of the origin of species. But these marks are demonstrably 

 of no use, since they are entirely covered by the epidermis 

 of the animal when alive, and absolutely invisible. Again, 

 some birds have slight differences in colour markings which 

 separate species. Now these differences may perhaps be re- 

 garded as of use as protective or as recognition marks. 

 But in some cases the colour markings are entirely con- 

 cealed by other feathers and, being invisible, can be of no 

 possible utility. It is hardly possible for one, unless he has 

 decided previously to accept the all-sufficiency of natural 

 selection, to believe that there can be any utility in the very 

 slight differences in the shape of leaves of plants, in the micro- 

 scopic markings of the hairs of different species of mammals, 

 the exact numbers of the feathers in the tails of birds, the 

 peculiar distribution of the veins in the wings of a butter- 

 fly, the microscopic markings in the scales on its wings, or 

 a host of other similar trivial characters. When it is re- 

 membered that the selection principle would force us to 

 insist that all of these characters are of value sufficient to 

 protect their possessors at the expense of other individuals 

 not possessing them, it is evident that the burden thrown 

 upon the principle of survival becomes very great. When 

 finally we come to characters of specific nature connected 

 with colour markings which are invisible when the animal 

 is alive, there is apparently no resource left except to con- 

 clude that the principle of survival because of utility does 

 not account for everything." 



It is indeed the general recognition by naturalists of the 

 fact of the triviality or indifference of a majority of specific 

 characters that has led to the recent renewal of the import- 

 ance of isolation theories, particularly of geographical 

 isolation. The rehabilitation of Moritz Wagner's theory of 

 species-forming by migration and isolation is a conspicuous 

 feature in present-day evolution discussion. The way in 

 which isolation comes to the aid of selection, or even sup- 



